An original polygraph machine which is hooked up to a plant to measures conductivity showed electrical reactions to 2 types of actions. Electronics were kept outside of a shipping container to block EM waves. One action was physical contact by hand or fire extinguisher blast. The other was intent to harm the plant without physical contact. Both showed electrical reaction consistent with a reaction from the plant and other explanations are unknown.
Some applications for these plant reactions could be to detect other living things or for people to interact with their plants. These signals can be frequency shifted to produce sounds as well. In related research, plants grow faster the louder the sound is in their environment and can be put to sleep with ether. Thought has been detected electrically which produces specific magnetic frequencies, so a possible theory is that plants pick up the magnetic currents which our understanding is limited on.
- MythBusters Want to Know If Tweeting to Plants Helps Them Grow Faster (urbantimes.co)
- Kirilian Photography, Trees Perception of Human Intention, Biocommunication Aura (lilianausvat.wordpress.com)